The National Institute on Drug Abuse (NIDA) is the largest single supporter of the world's research on drug abuse and addiction. NIDA seeks to contribute to the development of an international cadre of trained drug abuse scientists to collaborate on research and to conduct related activities to facilitate international research to address the problems of drug use, abuse and addiction in the United States and around the world. The International Research and Training Support Program (IRTS) was initiated as the International Visiting Scientist and Technical Exchange Program (INVEST) in 1990 by NIDA to promote the development of collaborative international research through fellowships, technical consultation and scientific information exchange. The IRTS Program has built upon this program and is designed to advance the global body of knowledge on drug abuse and related health consequences by (1) facilitating the development of an international network of drug abuse scientists who are knowledgeable about research on drug abuse and who will contribute to global knowledge about drug abuse; (2) developing and promoting opportunities to build international collaboration in prioritized areas of research on drug abuse and related health consequences; and (3) conducting a variety of activities designed to advance scientific knowledge on drug addiction.